1. Field of the Invention
This invention relates to a closure device of plastic which may be attached via a piercable location of a closed receptacle and which has a bung-like lower part with a cylindrical pour-out spout which is connected or connectable to the receptacle, and a screw cap which may be pushed onto the lower part, as well as a cylindrical piercing element which in the axial direction is open on both sides and which is displaceably mounted in the lower part, and during a screwing-off movement of the screw cap for the first time the piercing element moves helically downwards.
2. Discussion of Related Art
Closure devices of plastic and having three parts, as described above, and having a bung-like lower part with a cylindrical pour-out spout, of a cylindrical piercing element movable therein and a screw cap which moves the piercing element are known in varied forms. Such closure devices are attached to soft-packaging receptacles. The receptacles have multi-layered films which usually have one or more paper or cardboard layers, one or more plastic film layers and at least one blocking layer, for example of aluminium. In the region of the closure devices to be attached, the packaging has suitable pre-punched piercing locations. Usually, according to the piercing element of the closure device, only the innermost-lying compact plastic film layer and the aluminium layer need to be severed.
With most known forms the piercing element is designed so that the piercing element merely exerts a translatory movement towards the inside of the packaging. For example European Patent Reference EP-A-0,328,652 teaches a solution in which the screw cap has a guide-path-like helical line centrically incorporated on an inner wall, while the piercing element has a similar counter-running thread and simultaneously the piercing element has cams which prevent a rotation relative to the pour-out bung. A solution is also known from PCT International Publication WO 99/62776. Also Great Britain Patent Reference GB-2241224 teaches a closure device with a bung-like pour-out in which there runs a piercing element with guide cams, wherein the guide cams engage into axially running grooves and simultaneously the piercing element has an inner thread which cooperates with a centric annular wall of the screw cap, wherein the centric wall comprises an outer thread. Simultaneously, a threaded connection exists between the screw cap and the pour-out bung.
One solution taught by Great Britain Patent Reference GB-A-2241224 does not function with a piercable location in the packaging but the pour-out bung is welded from the inside to the inner wall of the packaging and an additional film is attached on the inside on the flange of the pour-out bung. Such a closure film may have any of properties which differ from the actual packaging. Accordingly, the piercing element may have practically any shape, for example as shown in FIG. 1 of this publication, or there may be several perforation teeth on the circumference of the piercing element. Completely analogous to this, in the embodiment according to European Patent Reference EP-A-0′328′652 there is a piercing element which has a multitude of perforation teeth on the lower edge, which is also the case with PCT International Publication WO 99/62776 which was mentioned.
In contrast, PCT International Publication WO 95/05996 shows a closure device in which the piercing element does not only carry out a purely translatory movement but also a screw movement. The piercing element comprises an outer thread which is meshingly guided into an inner thread in the pour-out bung. The piercing element may be set into a corresponding screw movement by a lug in the screw cap. If the screw cap is screwed off, then the piercing element moves simultaneously in a screw movement downwards into the receptacle to be opened. Also, the piercing element along its lower edge has a multitude of perforation teeth in a completely analogous manner to known devices.
Practically all known closure devices obtainable on the market today have significant problems. While initial solutions not documented here functioned practically without perforation teeth and with which the receptacle wall was destroyed somewhere, with perforation teeth it was believed that one could overcome the problem. This however was not the case. One of the main reasons is the fact that all known devices demand a large force effort on opening. Practically with all known devices, over the entire circumference many locations of the films are simultaneously perforated. If the teeth are located at exactly those locations which are vertically above the pre-separated film, then a solution would be possible. This however would demand a fastening of the closure device onto the receptacle which is exact to practically a tenth of a milimeter. This is simply not possible. Accordingly, the teeth also dig into regions of the packaging which are not pre-punched. Thus, not only is considerably more force required but also a pure pulling movement to the film is effected. While films mostly react sensitively to perforations, most films are extraordinarily resistant to tension forces.
The embodiment taught by PCT International Publication WO 95/05996, essentially a cutting effect is achieved instead of a piercing effect. Accordingly, the concept with a multitude of perforation teeth does not make sense. Also, with a small rotational angle the complete inner region is cut out of the packaging and falls into the contents of the receptacle. This is not only undesirable and unhygienic, but also during the pouring-out the loose part again and again gets into the pour-out region and leads to uncontrollable pour-out characteristics.